Refrigerating apparatus with defrosting means



y 1, 1962 L. J. MANN ETAL 3,031,859

REFRIGERATING APPARATUS WITH DEFROSTING MEANS Filed June 25. 1960 I Q j) 1 J) 4 6 i 5 w l 16 56 ii a [0 N J? 0 if 7 ,1 ;& 14 7 lanyard J. 277027)? j INVENTORS United States Patent 3,031,859 Patented May 1, 1962 Fice 3,031,859 REFRIGERATIWG APPARATUS WITH DEFROSTING MEANS Leonard J. Mann and Clifford H. Wurtz, Dayton, Ohio,

This invention pertains to refrigerating apparatus and more particularly to means for defrosting refrigerant evaporators.

Many ways of defrosting evaporators are known. In some, through the provision of suitable valves, hot gas is forced by the compressor through the evaporator. The use of such valves, however, is often objectionable.

In others, the cold refrigerant in or associated with the evaporator is heated to accomplish defrosting. In this latter type, much refrigeration and heat is wasted by heat ing the cold liquid.

It is an object of this invention to provide an arrangement wherein the relatively warm liquid at the outlet of the condenser can be used to defrost the evaporator.

It is another object of this invention to provide an arrangement wherein the heating of the relatively warm liquid at the outlet of the evaporator will force delivery to the evaporator of warm gas formed by the evaporation of the liquid to defrost the evaporator.

These and other objects are attained in the forms shown in the drawing in which a check valve is placed at the outlet of the condenser between the condenser and a receiver. An electric heater associated with the receiver is energized by suitable switch to further heat and evaporate the liquid in the receiver and to drive the evaporated liquid up through the capillary tube restrictor into the evaporator for defrosting the evaporator.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein preferred embodiments of the present invention are clearly shown.

In the drawings:

FIGURE 1 is a diagrammatic view of refrigerating system embodying one form of my invention;

FIGURE 2 is one form of wiring diagram for controlling the system shown in FIGURE 1; and

FIGURE 3 is another form of wiring diagram for controlling the system shown in FIGURE 1,

Referring to FIGURE 1, there is shown a sealed motorcornpressor unit 20 which first delivers compressed refrigerant to a superheat-removing coil 22 which returns the cooled refrigerant back to the sealed unit 20. From the sealed unit 20 the refrigerant then is forced into the condenser 24. At the outlet of the condenser 24, there is provided a check valve 26 which drains into the receiver 28. The receiver 28 is arranged to be heated by an electric heater 32 which is located in heat transfer relation with it. This electric heater, if desired, may extend inside the receiver 28 in contact with the liquid or it may be mounted upon and bonded to the outside of the receiver 28 in any suitable way so as to effectuate good heat transfer therewith. The electric heater 32 may be connected directly in series with a thermostat switch 34 which at times may open to prevent overheating of the receiver 28.

The top of the receiver 28 is connected to a supply conduit 36 extending to a filter drier member 38, in turn connecting through a capillary restrictor supply tube 40, with the evaporator 42 located within the compartment 44 to be cooled. The outlet of the evaporator '42 connects with a liquid trap 46, the top of which connects to the suction line 48 extending to the inlet of the sealed motorcompressor unit 20.

According to my invention, whenever .it is desired to defrost the evaporator 42, the sealed motor-compressor unit is stopped and the electric heater 3.2 is energized. This heats and evaporates the warm liquid refrigerant within the receiver 28 which is relatively warm at all times. This heating of the refrigerant causes gas to form under pressure in the top of the receiver which is forced through the capillary restrictor to the evaporator. The gas is prevented from going to the condenser by the closing of the check valve 26. The rise in pressure in the receiver forces the warm gas which has been raised in temperature by the heater 32 up through the supply conduit 36, the filter drier unit 38 and the capillary tube '40 into the evaporator =42, thereby warming the evaporator 42 and melting the frost therefrom. An excess liquid passing into the evaporator 42 or forced out of the evaporator 42 will be collected and held in the liquid trap 46.

The defrosting may be controlled by either of the systems shown in FIGURE 2 or FIGURE 3. In FIGURE 2, a switch, such as a thermostatic control switch 50, is connected directly in series with the electric compressor motor 20. To defrost the system, the switch so is opened and a switch 52 in series with the heater 32. is closed so that the heater 32 is energized. The energization of the heater 32 by the closing of the switch 52 effects the defrosting of the evaporator 42 as previously mentioned. At the termination of the defrosing of the evaporator 42, the switch 52 is opened and the switch 50 is closed to reenergize the sealed motor-compressor unit to draw evaporated refrigerant from the liquid trap 46 at the outlet of the evaporator 42 to begin the evaporation within the room to be cooled, designated by reference character 4-4. After the refrigerant is drawn from the liquid trap 46, additional refrigerant will be evaporated from the evap- 7 orator 42 at lower temperatures so as to resume cooling of the space 44.

In FIGURE 3, a double throw switch 54 is provided which normally engages the contact 56 to operate the sealed motor-compressor unit 20 to provide normal refrigeration. To accomplish defrosting, the double throw switch 54 is moved into contact with the contact 58 which connects to the defrost heater 32. The energization of the defrost heater 32 accomplishes defrosting of the evap orator '42 as previously explained. Should the receiver 28 rise too high in temperature, the thermostatic switch 34 which is in heat transfer relation with the top of the receiver will open for a sufiicient period of time to prevent overheating of the receiver after which it will automatically reclose.

Since the liquid which comes out of the condenser 24- is cooled by environmental air, the temperature of this environmental air will vary from about 70 to F. normally. Therefore, the temperature of the refrigerant within the receiver 28 also exposed to the environmental air will not be any lower than this. Therefore, this is warm enough to help accomplish the defrosting and the heater 32 is required to provide enough heat to force the refrigerant up into the evaporator 42 to accomplish derosting. This defrosting will be accomplished rapidly and effectively and, since the motor-compressor unit is not operating, no cooling will take place during this time except as provided by the frost upon the evaporator 42.

While the embodiments of the present invention as herein disclosed, constitute preferred forms, it is to be understood that other forms might be adopted.

What is claimed is as follows:

1. Refrigerating apparatus including a compressor and a condenser and a check valve and a receiver and a continuously open expansion device and an evaporating means connected in a closed refrigerant circuit arranged in series in the order named adapted to circulate a re frigerant, means for heating said receiver for forcing 3,0 3 Warm refrigerant through said expansion device into said evaporator to heat and defrost said evaporator, and means coinciding With the heating of said receiver for preventing operation of said compressor.

2. Refrigerating apparatus including a compressor and a condenser and a check valve and a receiver and a continuously open expansion device and an evaporating means connected in a closed refrigerant circuit arranged in series in the order named adapted to circulate a refrigerant, an electric heater associated in heat transfer relation with said receiver, switch means for energizing said electric heater to heat said receiver for forcing warm refrigerant through said expansion device into said evaporator to heat and defrost said evaporator, and means coincidental to the energizing of said electric heater for 15 preventing the operation of said compressor.

3. Refrigerating apparatus including a compressor and a condenser and a check valve and a receiver and a continuously open expansion device and an evaporating means connected in a closed refrigerant circuit in the order named adapted to circulate a refrigerant, an electric heater associated in heat transfer relation with said receiver, and switch means for energizing said electric heater to heat said receiver for forcing warm refrigerant through said expansion device into said evaporator to heat and defrost said evaporator and thermostatic switch means in series with said heater and responsive to the temperature of said receiver for limiting the heating thereof.

4. Refrigerating apparatus including a compressor and a condenser and a check valve and a receiver and a continuously open expansion device and an evaporating means connected in a closed refrigerant circuit arranged in series in the order named adapted to circulate a refrigerant, means for heating said receiver for forcing warm refrigerant through said expansion device into said evaporator to heat and defrost said evaporator, temperature responsive means responsive to the temperature of said receiver for limiting the heating of said receiver, and means coinciding With the heating of said receiver for preventing operation of said compressor.

Urban Oct. 3, 19'44 Zwickl Apr. 21, 1959 

